When creating melodies, bass runs or chords you will probably want to choose notes that fit the key you are working in.

If, like me, key theory doesn't come naturally to you here is a quick way to be sure that you can only choose notes which come from the key you are working in. 

This makes it a snip to focus on the creative work without having to stop and consider key theory.
Take the 'C minor' Midi file (or any other scale that you want to use) from Keys and chords and place it in the Session View.

Next select all the Midi notes and move them up or down until the Tonic (lowest note) matches the Key that you want to work in. For example moving to A# (Bb) will give you a key of Bb minor

Press 'Fold' to collapse all the notes. Select all the notes and use Shift up/down arrow to select a suitable range for your song.

Now delete all the notes and you are left with a grid which contains only the notes of the scale that you have chosen.

Now every note that you place in your song will be musically in-tune with your chosen scale.

Great for writing chords too.